CNOT Gates in Four-Qubit Fluxonium Systems Achieve Sub-100 ns Errors, Enabling Scalable Quantum Processors
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Achieving reliable quantum computation demands increasingly complex systems, yet maintaining low error rates as qubit numbers grow presents a significant challenge. Valeria Díaz Moreno, Nikola D. Dimitrov, and Vladimir E. Manucharyan, alongside Maxim G. Vavilov, investigated the performance of a four-qubit system built from inductively coupled fluxonium qubits, focusing on the impact of ‘spectator’ qubits, those not directly involved in a computation, on the fidelity of a crucial quantum gate. Their results demonstrate that carefully tuning the frequencies of these spectator qubits effectively suppresses errors, achieving gate errors below one percent for operations completed in under 100 nanoseconds. By exploiting the system’s local connectivity, the team projects these findings to larger qubit chains, offering a promising route towards building scalable and accurate quantum processors. Multi-Qubit CNOT Gates with Fluxoniums Researchers are advancing superconducting quantum computing by investigating multi-qubit systems built from fluxonium qubits. This work explores the performance of controlled-NOT (CNOT) gates in inductively coupled arrangements extending beyond just two qubits, addressing challenges of increased qubit connectivity and crosstalk.
The team focuses on maintaining high gate fidelity as the number of coupled qubits grows, developing strategies to minimize unwanted parasitic couplings and crowded frequency ranges. Careful design of the coupling network and precise control of qubit frequencies are crucial for achieving high-fidelity CNOT gates in multi-fluxonium systems, paving the way for more complex and scalable quantum circuits. This progress in understanding and controlling interactions between multiple fluxonium qubits is essential for building practical quantum processors. Scalable quantum processors require maintaining low error rates in substantially larger architectures. This work analyses a system of four inductively coupled fluxonium qubits to determine how the presence of additional qubits impacts CNOT gate performance. The results show that errors caused by these additional qubits are strongly suppressed when their transition frequencies are sufficiently detuned from those of the qubits actively performing the gate. Leveraging the locality of the nearest-neighbor coupling, the researchers extrapolate these findings to longer fluxonium chains, suggesting a pathway towards building more robust and scalable quantum computers.
Fluxonium Qubits Demonstrate Robust High Fidelity Researchers are demonstrating the potential of fluxonium qubits as a promising platform for building scalable and high-fidelity superconducting quantum computers. This work investigates the challenges and advancements in designing, controlling, and entangling these qubits, leveraging the unique properties of fluxoniums to overcome limitations of other qubit types. A significant emphasis is placed on minimizing errors and achieving high-fidelity two-qubit gates, such as CNOT gates. Fluxonium qubits, based on a Josephson junction shunted by a large inductor, are less sensitive to charge noise, a major source of decoherence. Researchers are focusing on achieving very low error rates in both single-qubit and two-qubit gates, crucial for building fault-tolerant quantum computers, and employing techniques like cross-resonance gates and tunable couplers. Unwanted interactions between qubits, known as ZZ coupling, can lead to errors, and the research explores methods to suppress or mitigate this effect using sophisticated modeling and simulation tools. Researchers have demonstrated millisecond coherence times in fluxonium qubits, a significant advancement, and stable CNOT gate performance over extended periods. Computer-aided design tools are utilized for quantization and numerical analysis of superconducting circuits to improve design and performance, implying that fluxonium qubits are a promising platform for scalable quantum computers. Investigating a chain of four inductively coupled fluxonium qubits, they found that carefully tuning the transition frequencies of spectator qubits, so they are sufficiently detuned from those actively involved in gate operations, significantly reduces errors. Specifically, the team achieved two-qubit gate errors below 10⁻⁴ for gate times of 100 nanoseconds, and below 10⁻³ for 50 nanoseconds, demonstrating that high-fidelity operations are indeed achievable in larger fluxonium systems. Because the coupling between qubits is limited to nearest neighbors, these principles extend to larger systems, offering a viable path toward scalable quantum processors. 👉 More information 🗞 CNOT gates in inductively coupled multi-fluxonium systems 🧠 ArXiv: https://arxiv.org/abs/2512.11756 Tags: Rohail T. As a quantum scientist exploring the frontiers of physics and technology. My work focuses on uncovering how quantum mechanics, computing, and emerging technologies are transforming our understanding of reality. I share research-driven insights that make complex ideas in quantum science clear, engaging, and relevant to the modern world. Latest Posts by Rohail T.: Non-universal Extinction Curves Impact Cepheid Distances, Introducing up to 40% Variation in Wesenheit Function Coefficients December 16, 2025 Seiberg-witten Theory Complexity Reveals Finite Descriptions for Effective Field Theories Using O-minimality December 16, 2025 Cognisnn Enables Neuron-Expandability and Dynamic-Configurability Via Random Graph Architectures in Spiking Neural Networks December 16, 2025